2024 day 18, part 1

It's super slow but I'll wait for optimization until I see what part 2 is...

README.md

@@ -5,8 +5,8 @@
 My Elixir solutions for [Advent of Code](https://adventofcode.com/) (all years).
 
 <!-- stars start -->
-<p><img src="https://img.shields.io/static/v1?label=Total&message=451%20stars&style=for-the-badge&color=green" alt="451 stars" /></p>
-<p><a href="./lib/y2024/"><img src="https://img.shields.io/static/v1?label=2024&message=32%20stars&style=for-the-badge&color=yellow" alt="32 stars" /></a><br />
+<p><img src="https://img.shields.io/static/v1?label=Total&message=452%20stars&style=for-the-badge&color=green" alt="452 stars" /></p>
+<p><a href="./lib/y2024/"><img src="https://img.shields.io/static/v1?label=2024&message=33%20stars&style=for-the-badge&color=yellow" alt="33 stars" /></a><br />
 <a href="./lib/y2023/"><img src="https://img.shields.io/static/v1?label=2023&message=44%20stars&style=for-the-badge&color=green" alt="44 stars" /></a><br />
 <a href="./lib/y2022/"><img src="https://img.shields.io/static/v1?label=2022&message=%E2%AD%90%EF%B8%8F%2050%20stars%20%E2%AD%90%EF%B8%8F&style=for-the-badge&color=brightgreen" alt="50 stars" /></a><br />
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lib/y2024/README.md

@@ -2,7 +2,7 @@
 
 My Elixir solutions for [Advent of Code 2024](https://adventofcode.com/2024).
 
-<!-- stars 2024 start --><img src="https://img.shields.io/static/v1?label=2024&message=32%20stars&style=for-the-badge&color=yellow" alt="32 stars" /><!-- stars 2024 end -->
+<!-- stars 2024 start --><img src="https://img.shields.io/static/v1?label=2024&message=33%20stars&style=for-the-badge&color=yellow" alt="33 stars" /><!-- stars 2024 end -->
 
 ## Benchmarks
 
@@ -46,4 +46,5 @@ day 15, part 1          5.06      197.80 ms     ±0.60%      197.59 ms      201.
 day 16, part 1         12.91       77.43 ms     ±5.49%       77.14 ms       86.71 ms
 day 16, part 2         13.07       76.51 ms     ±5.00%       76.09 ms       85.69 ms
 day 17, part 1       45.64 K       21.91 μs    ±15.81%       21.17 μs       37.50 μs
+day 18, part 1          0.27         3.73 s     ±0.03%         3.73 s         3.73 s
 ```

lib/y2024/day18.ex

@@ -0,0 +1,62 @@
+defmodule Y2024.Day18 do
+  use Advent.Day, no: 18
+
+  alias Advent.PathGrid
+
+  def part1(bytes, size \\ 50, byte_num \\ 1024) do
+    fallen = Enum.take(bytes, byte_num)
+
+    graph =
+      Enum.reduce(fallen, empty_grid({0, 0}, {size, size}), fn coord, graph ->
+        PathGrid.add_wall(graph, coord)
+      end)
+
+    length(Graph.get_shortest_path(graph, {0, 0}, {size, size})) - 1
+  end
+
+  # @doc """
+  # iex> Day18.part2("update or delete me")
+  # "update or delete me"
+  # """
+  # def part2(input) do
+  #   input
+  # end
+
+  @doc """
+  iex> Day18.parse_input("5,4\\n4,2\\n4,5\\n3,0\\n")
+  [{5,4}, {4,2}, {4,5}, {3,0}]
+  """
+  def parse_input(input) do
+    input
+    |> String.split("\n", trim: true)
+    |> Enum.map(fn line ->
+      [left, right] = String.split(line, ",", parts: 2)
+      {String.to_integer(left), String.to_integer(right)}
+    end)
+  end
+
+  @doc """
+  Create a completely empty path grid of a given size.
+  """
+  def empty_grid({from_row, from_col}, {to_row, to_col}) do
+    Enum.reduce(from_row..to_row, Graph.new(vertex_identifier: & &1), fn row, graph ->
+      Enum.reduce(from_col..to_col, graph, fn col, graph ->
+        graph = Graph.add_vertex(graph, {row, col}, :floor)
+
+        [{row - 1, col}, {row, col - 1}]
+        |> Enum.reduce(graph, fn neighbour, graph ->
+          if PathGrid.floor?(graph, neighbour) do
+            graph
+            |> Graph.add_edge({row, col}, neighbour)
+            |> Graph.add_edge(neighbour, {row, col})
+          else
+            graph
+          end
+        end)
+      end)
+    end)
+  end
+
+  def part1_verify, do: input() |> parse_input() |> part1(70, 1024)
+  # def part2_verify, do: input() |> parse_input() |> part2()
+end

test/y2024/day18_test.exs

@@ -0,0 +1,14 @@
+defmodule Y2024.Day18Test do
+  use ExUnit.Case, async: true
+  alias Y2024.Day18
+  doctest Day18
+
+  test "part1" do
+    assert test_data() |> Day18.parse_input() |> Day18.part1(6, 12) == 22
+  end
+
+  test "verification, part 1", do: assert(Day18.part1_verify() == 436)
+  # test "verification, part 2", do: assert(Day18.part2_verify() == "update or delete me")
+
+  def test_data(), do: File.read!("test/y2024/input/day18/sample.txt")
+end